Electrical Stimulation of the Rectus Femoris During Pre-swing Diminishes Hip and Knee Flexion During the Swing Phase of Normal Gait

Abstract

Individuals who have suffered cerebral insults often exhibit stiff-knee gait, a condition characterized by reduced knee flexion during swing. We investigated the effect that an increment in normal rectus femoris (RF) activity can have on hip and knee joint angles during swing, as a first step to determining this muscle's involvement in stiff-knee gait. For this, we developed a protocol that electrically stimulated the RF during pre-swing or after toe-off in randomly selected strides of treadmill walking, consistent with the timing of RF activity during normal gait. Seven healthy young adults participated in the study. Pre-swing stimulation induced a significant (p<0.05) reduction in peak knee flexion (avg 7.5deg) in all subjects, with an accompanying decrease in hip flexion in four of the subjects. RF stimulation after toe-off diminished peak knee flexion in three subjects and reduced hip flexion in four subjects. When compared to muscleactuated gait simulations that were similarly perturbed, the induced motion measures were generally consistent in direction but exhibited greater variability across strides and subjects. We conclude that excess RF activity during pre-swing has the potential to contribute to stiff-knee gait, and that clinical treatment should consider the "counter-intuitive" function that the RF has in extending the hip.

Empirical evaluation of gastrocnemius and soleus function during walking

“…Induced accelerations characterize the instantaneous capacity of a muscle to generate accelerations, which is dependent on the current posture but independent of other muscles. In contrast, our forward dynamics simulations measure changes in joint position, which evolve over time and therefore include the effect of biomechanical and neural interactions (Anderson et al, 2004; Hernandez et al, 2010). …”

“…During post-processing, EMG activities during cycles before and during stimulation were rectified. To evaluate spill-over, we quantified induced muscle activities by integrating rectified EMG between stimulus pulses, after a brief time period to allow for the direct stimulation pulse effects to dissipate on each electrode (Hernandez et al, 2010) (Fig. 2).…”

A Muscle’s Force Depends on the Recruitment Patterns of Its Fibers

“…Recently, several studies have attempted to validate scaled length–tension relationships for whole muscles, 68 to simulate the three-dimensional geometry of muscles during contraction, 7 and to qualitatively confirm the actions of select muscles predicted by simulations. 27 However, the accuracy with which traditional, Hill-type models predict muscle forces during in vivo activities remains untested.…”

Coordination of the non-paretic leg during hemiparetic gait: Expected and novel compensatory patterns

“…Furthermore, RF tends to decrease the peak knee flexion velocity (Goldberg et al 2004; Goldberg et al 2006) and over activity during region 4 and swing is often implicated in stiff knee gait (Goldberg et al 2004). Additionally, Hernandez et al (2010) in their electrical stimulation study reported that RF stimulation before the toe-off largely reduced the peak knee flexion during swing as opposed to the stimulation during the swing phase. Reduced propulsion due to increased activity of RF in the non-paretic leg is further supported by reduced propulsive impulse generation during region 4 of stance phase, specifically in moderate and fast speed groups.…”